The present invention relates to an interchangeable part for a workpiece fixture, in particular of gear cutting machines, and to a workpiece fixture adapted to the interchangeable part and to a system comprising interchangeable part and workpiece fixture.
Workpiece fixtures are used to fix a workpiece in a given position for machining. The higher the requirements for machining precision are, the more expensive such workpiece fixtures are. This holds in particular for workpiece fixtures for gear cutting machines. Therefore one normally attempts to construct workpiece fixtures so that they can fix a plurality of different workpieces. This requires interchangeable parts which are inserted as intermediate parts between the workpiece to be clamped and the workpiece fixture. A first end of such an interchangeable part is specially adapted for receiving a specific type of workpiece and a second end of the interchangeable part is used for fixing the interchangeable part on the workpiece fixture.
Usually, said interchangeable parts are connected firmly with the workpiece fixture by screws. Reliable connection of the interchangeable part with the workpiece fixture is necessary for functional reasons because otherwise the adhesive effect of the coolant used in the machining process leads to the danger of the interchangeable part sticking to the finished workpiece upon removal of the latter from the machining tool. However, when the workpiece fixture is changed over from one type of workpiece to another type of workpiece the screw connection involves considerable effort and accordingly long change-over times due to the loosening and retightening of the screws. The resulting production downtimes are cost-intensive and therefore undesirable.
The present invention is based on the problem of proposing an interchangeable part for a workpiece fixture and a workpiece fixture adapted to such an interchangeable part which ensure reliable connection between interchangeable part and workpiece fixture, on the one hand, and rapid replacement of interchangeable parts, on the other hand.
The invention relates to two essential aspects or elements which are each realized partially in the interchangeable part and partially in the workpiece fixture and adapted to each other so as to permit optimal cooperation. Specifically, the one essential aspect is a locking connection between the interchangeable part and the workpiece fixture to ensure that the interchangeable part is firmly connected with the workpiece fixture after being locked in. The other essential aspect is a force amplifying device for releasing the locked-in interchangeable part from the workpiece fixture when one interchangeable part is to be replaced by another interchangeable part.
The locking connection includes two locking elements, one on the interchangeable part and the other on the workpiece fixture, which cooperate so as to permit separation of the locked-in interchangeable part from the workpiece fixture only if a minimum force is overcome. Specifically, the locking elements can be formed as a depression or groove, on the one hand, and an elastically deformable element, such as a spring-loaded pin, engaging the depression or groove, on the other hand. It is irrelevant whether the depression/groove or the elastically deformable element is mounted on the interchangeable part. For reasons of design and cost, however, it is preferable to provide the depression or groove, which can be produced in simple and space-saving fashion, on the interchangeable parts and integrate the elastically deformable element, which is more elaborate and larger in contrast, in the workpiece fixture.
The force amplifying device is realized on a face of the end of the interchangeable part used for fixation on the workpiece fixture, in the form of at least one ramp extending in the circumferential direction relative to a rotation axis, whereby at least one stop face or stop pin is disposed on the workpiece fixture opposite said ramp in order to cooperate with the ramp of the interchangeable part. In the locked condition the face of the interchangeable part lies against the stop face or stop pin or is directly adjacent thereto. Upon rotation of the locked interchangeable part about the rotation axis, an axial force acting in the direction of the rotation axis is then applied to the stop face or stop pin of the workpiece fixture via the inclined ramp surface. This leads to displacement of the interchangeable part in the axial direction relative to the workpiece fixture, thereby releasing the locking connection under constraint. The flatter the inclination of the ramp is selected, the greater the angle of rotation is about which the locking element must be rotated for release from the workpiece fixture, but the lower the force is which must be applied for overcoming the biasing force of the locking connection.
Preferably a plurality of ramps are uniformly distributed concentrically about the rotation axis on the face of the interchangeable part, and preferably an equal number of stop pins are uniformly distributed in the circumferential direction over the cylindrical surface of the workpiece fixture. This ensures uniform force distribution relative to the rotation axis and avoids jamming of the interchangeable part on the workpiece fixture upon release of the connection. The smallest ramp inclination and accordingly the lowest necessary expenditure of force for releasing the interchangeable part from the workpiece fixture results when the ramps distributed uniformly over the face of the interchangeable part are adjacent and form notches and prongs. The root of the notches is preferably slightly lower than the imaginary intersection point of the adjoining ramps, which makes the moment of locking clearly perceptible.